1. Field of the Invention
Embodiments described herein relate generally to a hologram transfer foil which is easy to identify and difficult to counterfeit and tamper, a fabrication method of an image display element, an image display element, and a personal authentication medium.
2. Description of the Related Art
In most of personal identification media such as passports or ID (identification) cards, face images are used in order that personal authentication can be visually performed. For example, in a general passport, printing paper on which a face image is printed is attached to a booklet. However, there is a concern that such a passport is tampered by re-attaching a photoprint.
For this reason, in recent years, the information of a face image is digitized, and the digital information is reproduced on the booklet. As an image display technique which is used for image reproduction, use is made of, for example, a thermal transfer recording method by a transfer ribbon using a sublimation (thermal migratory) dye, or a resin melting type or wax melting type in which pigments are dispersed, or an electrophotography technique.
In recent years, printers by a thermal transfer recording method using a sublimation dye or a colored thermoplastic resin have been gaining in popularity. If this thermal transfer recording method is used, it is not necessarily difficult to remove a face image from a passport and to record another face image on the corresponding part.
On the other hand, there has been proposed a fluorescent printed matter on which a face image is printed by using the above-described image display technique and a face image is recorded thereon by using fluorescent ink (see, e.g. literature 1 (Jpn. Pat. Appin. KOKAI Publication No. 2000-141863)). In addition, there have been proposed an anti-counterfeit image formation element on which a face image is recorded by using ink which contains a colorless or thin-color fluorescent dye and a color pigment (e.g. literature 2 (Jpn. Pat. Appin. KOKAI Publication No. 2002-226740)), and a personal authentication medium on which an ordinary face image and a face image, which is formed by using a pearl pigment are disposed in juxtaposition (see, e.g. literature 3 (Jpn. Pat. Appin. KOKAI Publication No. 2003-170685)).
By applying the above-described image display techniques to passports, tampering of passports becomes more difficult.
However, a face image, which is recorded by using a fluorescent material, cannot be observed unless a special light source, such as an ultraviolet lamp, is used. In addition, although a face image, which is formed by using a pearl pigment, can be recognized by the naked eye, it is difficult to form an image with high fineness by using the pearl pigment since the grain size of the pearl pigment is large.
Tampering of a face is easier in a case where the look of a face image recorded on a personal authentication medium is simple and there is no special visual effect, than in a case where a face image is complex and has a characteristic visual effect. In addition, in a case where a face image is displayed with a simple look, it is difficult to visually determine with ease a counterfeited or tampered face image.